The present invention generally relates to polymer compositions containing phosphorus-nitrogen units on non-polyphosphazene backbones and methods of manufacture thereof, which provide a more economical alternative to pure polyphosphazene polymers.
The incorporation of phosphorus-containing components into organic polymers is a subject of general interest because such systems offer the promise of fire retardance and enhanced thermal stability as well as resistance to oxidation by molecular oxygen (Kumar, et al., Macromolecules, 28:6323 (1995); Kumar, et al., Macromolecules, 16:1250 (1983)). Numerous methods have been explored to synthesize such hybrid macromolecules. For example, poly(vinyl-phosphine oxides) have been examined in some detail (Rabinowitz, et al., J. Poly. Sci. Part A: Poly. Chem., 2:1233 (1964)). However, the linkage of phosphorus-nitrogen compounds to organic polymers offers some special advantages because of the synergistic fire retardance of phosphorus and nitrogen (Chamberlain in Flame Retardancy of Polymeric Materials (Kuryla and Papa, eds.), Vol. 4. (Marcel Dekker: New York, 1978)), and the overall stability under ambient conditions of species such as phosphazenes.
Small-molecule cyclic or linear phosphazenes can be incorporated into polymers in several ways. First, phosphazene rings may be linked through organic groups to yield cyclo-linear materials. These polymers incorporate a cyclic phosphazene trimer or tetramer directly into the backbone (Kumar, et al., Macromolecules, 28:6323 (1995); Kumar, et al., Macromolecules, 16:1250 (1983); Laszkiewicz, et al., Angew. Makromol. Chem., 99:1 (1981); Kajiwara, J. Macromol. Sci.-Chem., A16(2):587 (1981); Kajiwara, Angew. Makromol. Chem., 37:141 (1974); Allcock, Phosphorous-Nitrogen Compounds (Academic Press: New York, 1972); Sharts, et al., Inorg. Chem. 5:2140 (1966); Bilbo, et al., J. Poly. Sci. Part A; Poly. Chem., 5:2891 (1967); Tunca, et al. J. Poly. Sci. Part A: Poly. Chem., 36:1227 (1988); Chen-Yang, et al., Phosphorous, Sulfur, Silicon, 76:261 (1993); Kumar, J. Poly. Sci. Part A: Poly. Chem., 23:1661 (1985)). Of special interest are cyclo-linear species that are linked together via azide coupling reactions (Sharts, et al., Inorg. Chem., 5:2140 (1966); Bilbo, et al., J. Poly. Sci. Part A; Poly. Chem., 5:2891 (1967)). However, the difficulty involved in synthesizing high molecular weight polymers of this type, and the poor control of the molecular weight are major drawbacks. These problems can be solved by using a second approach, where vinyl or allyl compounds that bear cyclic phosphazene side groups are subjected to free radical addition polymerization or copolymerization to yield organic polymers with cyclophosphazene side groups (Allen, et al., Macromolecules, 21:2653 (1988)). In this case, the phosphazene ring is incorporated as a pendent side group rather than as part of the polymer backbone. Similar species have recently been prepared through the ring opening metathesis polymerization of norbornenes with cyclic phosphazene side units (Allcock, et al. Macromolecules, 32:7719 (1999)).
The incorporation of phosphorus atoms into organic polymers normally has the effect of decreasing their flammability (Green, J. Fire Sciences, 14:353-66 (1996)). Phosphazenes provide an excellent vehicle for the introduction of phosphorus into macromolecules. Cyclic phosphazene trimers have been incorporated into organic polymers in various ways. Researchers have demonstrated the homo- and copolymerization of cyclotriphosphazenes that bear an unsaturated side group via addition polymerization (Allen, Trends Polym. Sci., 2:10, 342-49 (1994); Inoue, et al., J. Polym. Sci. A: Polym. Chem., 30:145-48 (1992); Bosscher, et al., J. Inorg. Organomet. Polym., 6:3, 255-65 (1996); Selveraj, et al., Polymer, 38:3617-23 (1997); Allcock. et al., Macromolecules, 32:7719-25 (1999)). Others have incorporated cyclic trimers into condensation polymers using difunctional species (Dez, et al., Polym. Deg. Stab., 64:433-37 (1999); Tunca, et al., J. Polym. Sci. A: Polym. Chem., 36:1227-32 (1998); Radhakrishnan Nair, et al., Eur. Polym. J. 32:1415-20; Chen-Yang, et al., Phos. Sulf. Silicon., 76:261-64 (1993)). The drawback to both of these approaches is the need to study the polymerization behavior of each individual phosphazene monomer because the reactivity is affected both by the nature of the polymerizable group or groups and by the steric and electronic effects of the remaining side groups on the trimer.
It would be advantageous to provide improved methods for incorporating phosphorus-containing components into a range of organic polymers.
It is therefore an object of this invention to provide improved methods for incorporating phosphorus-containing components into a range of organic polymers.
It is another object of the present invention to provide a variety of phosphorus-containing organic polymers.
It is a further object of the present invention to provide phosphorus-containing organic polymers having improved fire retardant properties for use in a variety of applications.
It is still another object of the present invention to provide improved methods for incorporating phosphazenes into silicone polymers.
Methods have been developed to produce phosphazene modified organic or siloxane polymers. The method includes (a) providing an organic or siloxane polymer comprising phosphine units, and (b) reacting the organic or siloxane polymer with a phosphazene azide compound under conditions wherein the phosphazene azide compound is bound to the phosphine units in the polymer, thereby producing the phosphazene-modified organic or siloxane polymer. The organic polymer of step (a) is produced by reacting a first monomer comprising phosphine with a second monomer via free radical or anionic polymerization techniques to produce the organic polymer comprising phosphine units. The first and second monomers can be identical. A wide variety of organic polymer backbones can be modified using these techniques. The second monomer, for example, can be selected from monomers forming polyolefins, polydienes, polyacrylics, polyethylenes, polyvinyl chlorides, isoprenes, polystyrenes, polycaprolactam, poly(methyl methacrylate) and other poly-acrylates, and polypropylenes. Alternatively, the siloxane polymer of step (a) is produced by reacting a monomer comprising phosphine with a hydrosilicone polymer via hydrosilylation synthetic techniques to produce the siloxane polymer comprising phosphine units. These phosphazene modified organic and siloxane polymers are useful in a variety of applications, such as a fire retardant material, as demonstrated by the examples.